1. Field of the Invention
The invention relates to a method and apparatus for cleaning photoreceptor substrates. More particularly, the invention relates to an efficient cleaning method and apparatus that reduces the cost of the cleaning process, eliminates use of solvents or CFC's, is useful in cleaning photoreceptor substrates (metallic or plastic rigid cylinders, metallic or plastic flexible seamless belts, and the like) and, for that matter, any smooth surface object subject to strict cleanliness standards during manufacture, thereby reducing the unit manufacturing cost by virtue of this simplified cleaning process.
2. Description of Related Art
A photoreceptor is a cylinder or belt-like device used in a xerographic apparatus. The photoreceptor substrate is coated with one or more layers of a photoconductive material, i.e., a material whose electrical conductivity changes upon illumination. In xerographic use, an electrical potential is applied across the photoconductive layer and then exposed to light from an image. The electrical potential of the photoconductive layer decays at the portions irradiated by the light from the image, leaving a distribution of electrostatic charge corresponding to the dark areas of the projecting image. The electrostatic latent image is made visible by development with a suitable powder. Better control of the coating quality yields better imaging performance.
The coating of a substrate is generally accomplished through an automated four step process, whereby the substrate to be coated is first loaded on a support arm structure (Step 1) which then moves the substrate to successive processing stations. The substrate is first moved to the cleaning station (Step 2) which includes a cleaning chamber for receiving the support arm bearing the substrate and having decontaminating means for removing contaminants from the substrate; and then on to a coating station (Step 3) which includes a coating chamber for receiving the support arm bearing the substrate and having an applicator for applying a coating formulation onto the substrate. Finally, the substrate is moved to a curing station (Step 4) which includes a curing chamber for receiving the support arm bearing the coated substrate and has curing means for curing the coating on the substrate. An apparatus and method for processing as described above, is detailed generally in U.S. Pat. Nos. 5,032,052 (Swain), 5,038,707 (Swain et al.) and 4,747,992 (Sypula et al.) which are referenced here for purposes of describing a substrate coating and manufacturing process. In addition, as well known in the art, other suitable methods for coating photoconductive layers can be utilized, such as dip coating, vacuum deposition and the like.
Primary cleaning, an initial step in the photoreceptor coating process described above, is the key to obtaining the aforementioned high yield with reduced manufacturing costs. Processes currently in use employ some combination of mechanical brush, liquid detergents, freon or ozone sprays with simultaneous exposure to ultraviolet light, ultrasonic and/or vapor cleaning. In whatever combination, it is a costly and complex operation which inevitably will require altering since freon/CFC's will eventually be banned. The method and apparatus proposed herein will replace part or all of the existing photoreceptor cleaning methods and perhaps most importantly, will be available for future cleaning applications (i.e., seamless flexible belt substrates, plastic rigid substrates and any other smooth surface critical parts, such as semiconductor substrates) which require extreme cleanliness during manufacture.